Flat displays such as liquid crystal displays are widely used in, for example, computer displays, televisions, car navigation devices, portable information terminals, and mobile telephones.
In portable devices such as a mobile telephone or a portable information terminal, in vehicle-mounted equipment such as a car navigation device, and in some computers, a transparent protective plate is placed on an image display surface of a display panel. The protective plate prevents the image display surface of the display panel from being scratched and becoming difficult to view, and also prevents the display panel from being damaged even when dropped or subjected to a large impact.
The protective plate is generally set together with the casing of an electronic device when the electronic device is assembled. Therefore, it has heretofore been the case that there is a clearance between the protective plate and the display panel.
It has recently been suggested to directly attach the protective plate to the image display surface of the liquid crystal display panel via a bonding layer. This addresses the problem of the reflection in a glass surface caused by the presence of an air layer between the protective plate and the display panel. As a result, high-quality images can be displayed, and the manufacturing costs can be reduced by the reduction of the number of processes.
The protective plate can be bonded to the bonding layer by dropping, for example, a UV-curable adhesive coating solution to one of the protective plate and the bonding layer to attach the protective plate and the bonding layer to each other before the UV-cure of the solution. During the bonding, the formation of air bubbles in the bonding layer is prevented and the thickness of the bonding layer is minimized and made uniform so that high-quality images can be displayed. However, if the protective plate and the bonding layer are pressed to adjust the thickness of the bonding layer after the attachment, the spread of the forcibly crammed adhesive coating solution may not be stopped by surface tension and its viscosity, and the solution may run out of the space between the protective plate and the bonding layer and adhere to the display panel, leading to the deterioration of image quality. Thus, it has heretofore been the case that the protective plate and the bonding layer are attached to each other via the UV-curable adhesive coating solution, and are left after weakly pressed so that the UV-curable adhesive coating solution naturally spreads between the protective plate and the bonding layer to reduce the residual stress of the adhesive coating solution resulting from the pressing. It has therefore been difficult to further reduce the thickness of the bonding layer.